The lens matters a lot in a comparison between cameras. I don't know if Fujis are sharper than Olympus E-M whatever, but I really would expect the differences to be so small that it could be a matter of lens sharpness. That, and JPEG processing. I'm not a Nikon user anymore (I only have Fuji gear), but awhile back, Nikon and Pentax were well known for processing photos in such a way that the JPEGs weren't as sharp as they could be. However, it only reflected the choices that Nikon made with regards to in-camera processing of RAW data. It had nothing to do with the capabilities of the sensor.